If an edit were available here, that would be nice.
I had one tech, after months of messing around calling the stupid ISP every week. Them replacing.. everything. Who got in via the backdoor remotely from his service van.
He recorded everything done by us, watched everything the modem was doing, all this from his house while he was asleep.
A very old guy who looked like Santa Claus. This was after spending a few weeks ripping up underground lines and replacing them and all kinds of expensive stuff.
Once he got access and watched what was going on, he found the real problem. The interface card at the main connection 2 miles away.
That took all of one day.
Since we moved here to the outback desert, the internet hasnt worked at all. Dropping every few minutes, the phone just as bad.
It took 2 years of service calls to the ISP to get this thing working properly.
And, yet another one, who can and will connect to your modem, on the sly. To find out the real issue.
He finally fixed it too. Nice stable telephone and internet connection.
Same problem, the card at the interface 1.25 miles away, was toast.
For some reason, providers hate the idea of changing the card.
It practically requires taking out guns and holding them hostage.
They will spend thousands of dollars to change everything, with no result. The most likely point of failure is last.
Anyway, backdoors exist in modems. The techs who know wtf they are doing use them all the time, no doubt so do hackers.